PUBLIC HEALTH ASSESSMENT
FAIRCHILD AIR FORCE BASE
SPOKANE, SPOKANE COUNTY, WASHINGTON
PATHWAYS ANALYSIS/PUBLIC HEALTH IMPLICATIONS
The following section discusses the various contaminants ofconcern, how people might come into contact with thesecontaminants and the potential health effects that mayresult. In order for an exposure to these contaminants tooccur, all the elements of an exposure pathway must be inplace. Exposure pathways are divided into completed andpotential and can be current, past or future. A completedexposure pathway consists of five elements: source,environmental media/transport, point of exposure, route ofexposure and receptor population. A potential exposurepathway exists when some but not all of these five elementsare present and the potential exists that the missingelement(s) have been present, are present or will be present. The completed and potential exposure pathways forFairchild are given in Tables 2 and 3 below. Each pathway is then discussed in terms of thecontaminants of concern and the potential health hazard posed.
Evaluating Non-cancer Risk
In order to evaluate the potential for non-cancer adverse health effects to result from exposure tocontaminated media (i.e., air, water, soil, and sediment), a dose is estimated for each contaminantof concern. These doses are calculated for situations (scenarios) in which nearby residents or on-base workers might come into contact with the contaminated media. The estimated dose for eachcontaminant under each scenario is then compared to ATSDR's minimal risk level (MRL) or EPA'soral reference dose (RfD). MRLs and RfDs are doses below which non-cancer adversehealtheffects are not expected to occur (so called "safe" doses). They are derived from toxic effect levelsobtained from human population and laboratory animal studies. These toxic effect levels can beeither the lowest observed adverse effect level (LOAEL) or a no-observed adverse effect level(NOAEL). In human or animal studies, the LOAEL is the lowest dose at which an adverse health effect is seen, while the NOAEL is the highest dose that did not result in any adversehealth effects.
Because of the uncertainty in these data, the toxic effect level is divided by "safety factors" givingthe lower and more protective MRL or RfD. If a dose exceeds the MRL or RfD, this indicates onlythe potential for adverse health effects. The magnitude of this potential can be inferred from thedegree to which this value is exceeded. If the estimated exposure dose is only slightly above theMRL or RfD, then that dose will fall well below the toxic effect level. The higher the estimateddose is above the MRL or RfD, the closer it will be to the toxic effect level.
Evaluating Cancer Risk
Some chemicals have the ability to cause cancer. Cancer risk is estimated by calculating a dosesimilar to that described above and multiplying it by a cancer potency factor, also known as thecancer slope factor. Some cancer potency factors are derived from human population data. Othersare derived from laboratory animal studies involving doses much higher than are encountered in theenvironment. Use of animal data require extrapolation of the cancer potency obtained from thesehigh dose studies down to real-world exposures. This process involves much uncertainty. Currentthinking suggests that there is no "safe dose" of a carcinogen and that a very small dose of acarcinogen will give a very small cancer risk. Cancer risk estimates are, therefore, not yes/noanswers but measures of chance (probability). Such measures, however uncertain, are useful indetermining the magnitude of a cancer threat since any level of a carcinogenic contaminant carriesan associated risk. The validity of the "no safe dose" assumption for cancer-causing chemicals isnot clear. Some evidence suggests that certain chemicals considered to be carcinogenic mustexceed a threshold of tolerance before initiating cancer.
This document describes cancer risk qualitatively using terms like low, very low, slight and nosignificant increase in cancer risk. These terms can be better understood by considering thepopulation size required for such an estimate to result in a single cancer case. For example, a lowincrease in cancer risk indicates an estimate in the range of one cancer case per ten thousandpersons exposed over a lifetime. A very low estimate might result in one cancer case per severaltens of thousands exposed over a lifetime and a slight estimate would require an exposedpopulation of several hundreds of thousands to result in a single case. DOH considers cancer riskto be not significant when the estimate results in less than one cancer per one million exposed overa lifetime. The reader should note that these estimates are for excess cancers that might result inaddition to those normally expected in an unexposed population.
Cancer is a common illness that increases with age. Depending on the type of cancer, anunexposed population could be expected to have a substantial number of cancer cases. There aremany different forms of cancer that result from a variety of causes. About a quarter of the people in Washington State die of cancer. Approximately one quarter to one third of people living in the United States will develop cancer at some point in their lives.
Multiple Exposure and Toxicological Mixtures
A person can be exposed by more than one pathway and to more than one chemical. Exposure tomultiple pathways occurs if a contaminant is present in more than one medium (i.e., air, soil,surface water, groundwater, and sediment). For example, the dose of a contaminant receivedfrom drinking water may be combined with the dose received from contact with that same contaminant in soil.
It is much more difficult, however, to assess exposure to multiple chemicals. In almost everysituation of environmental exposure, there are multiple contaminants to consider. The potentialexists for these chemicals to interact in the body and increase or decrease the potential for adversehealth effects. The vast number of chemicals in the environment make it impossible to measure allof the possible interactions between these chemicals. Individual cancer risk estimates can beadded since they are measures of probability. When estimating non-cancer risk, however,similarities must exist between the chemicals if the doses are to be added. Groups of chemicalsthat have similar toxic effects can be added such as volatile organic compounds (VOCs) whichcause liver toxicity. Polycyclic aromatic hydrocarbons (PAHs) are another group of chemicalsthat can be assessed as one added dose based on similarities in chemical structure and metabolites. Although some chemicals can interact to cause a toxic effect that is greater than the added effect,there is little evidence demonstrating this at concentrations commonly found in the environment.
The following evaluations do not rely solely on whether the estimated dose of a contaminantexceeds its health comparison value or acceptable cancer risk level. Factors such as backgroundexposure, a growing scientific data base and the inherent uncertainty in assessing health risk areconsidered when formulating conclusions. These evaluations are based on current data andsubject to change should more data become available relative to the site and/or the toxic potentialof the contaminants.
Table 2. COMPLETED EXPOSURE PATHWAYS FOR FAIRCHILD AIR FORCE BASE, WASHINGTON
Non-cancer Â Â Â Cancer
|1a||Craig RoadLandfill||TCE, Nitrate a||Craig RoadLandfill|
|Groundwater||Vietzke Villagewater supply wells||Ingestion|
|Vietzke Villageresidents||1000||Past||Low||Slight||Water supply wellsabandoned. Past exposureof concern.|
|Airway Heightswater supply wells ||Ingestion|
|Airway Heightsresidents||4000||Past||No||NotSignificant||Low levels of TCE.Current monitoring.|
|Scafco watersupply wells||Ingestion||Scafcoemployees||50||Past||No||NotSignificant||Water supply wellsabandoned.|
|1b||Craig RoadLandfill||VOC||Craig Road|
|Air||Outdoor air nearVietzke Village||Inhalation||Vietzke Villageresidents||1000||Past ||No||NotSignificant||Low levels of VOCs.Current monitoring.|
|Groundwater||West Thorpe Roadresidential wells ||Ingestion|
|West ThorpeRoad residents||100||Past||No||NotSignificant||Low levels of TCE.Current monitoring.|
|3|| No-NameDitch(FairchildEasement)||TPH, Metals||Wastewaterlagoons|
| No-Name Ditch(FairchildEasement)||Ingestion|
|West ThorpeRoad residents||100||Past||No||NotSignificant||No comment.|
|Groundwater||West Thorpe Roadresidential wells ||Ingestion|
|West ThorpeRoad residents||100||Past ||No||NotSignificant||No comment.|
County Route 902
|West ThorpeRoad residents||<100||Past ||No||NotSignificant||No comment.|
|5||On-baseActivities||VOC, TPH,PCB, metals||P-1, P-2 and|
|Sediment/Soil||P-1, P-2 and|
|On-baseworkers||200||Past||No||NotSignificant||Areas of contaminationinfrequently accessed.|
|On-baseRecreators||200||Past ||No||NotSignificant||Low levels of lead in soil.|
a = Nitrate is discussed in this pathway relative to the Vietzke Village supply wells but is not thought to be related to the Craig Road Landfill.
b = The number of persons exposed is an estimate base on demographic data obtained from ATSDR and other sources.
Table 3. POTENTIAL EXPOSURE PATHWAYS FOR FAIRCHILD AIR FORCE BASE, WASHINGTON
| || |
|# ||Pathway |
|Contaminant ||Source ||Environmental |
|Point of |
| Route of |
|Time ||Comments |
|1 ||Future Off-Base Development ||VOC ||SW-8, WW-1, FT-1 ||Groundwater ||NA ||Ingestion |
|Residents, workers ||Future ||Groundwater on abutting property is not suitable for domestic use. |
|2 ||Future On-Base Development ||VOC, TPH ||Priority-1, 2 and 3 sites ||Groundwater ||NA ||Ingestion |
|Workers Residents ||Future ||Groundwater in many areas of the base is not suitable for domestic use. |
|Soil ||NA ||Ingestion |
|Residents ||Future ||Some on-base areas are currently not suitable for high exposure activities (e.g., residential development). |
|3 ||Base Supply Well #2 ||VOC, TPH ||NA ||Groundwater ||Base Residential and Building Taps ||Ingestion |
|Base workers and residents ||Future ||Site SW-13 (EOD range) represents a potential source of groundwater contamination. |
NA = Not applicable. These components are not currently present.
B. Completed Exposure Pathways
Completed exposure pathways are discussed below. A summary, background, health assessment,conclusions, and recommendations are provided for each pathway. The health assessment isseparated into a discussion of non-cancer and cancer effects.
|Pathway 1a: Craig Road Landfill --> Groundwater --> Vietzke Village Residents/Airway Heights Residents/Scafco Employees|
The Craig Road Landfill is the source of TCE groundwater contamination that has been found inVietzke Village public supply wells and the Scafco Corporation facility supply well. It is also apossible source of TCE contamination in the Airway Heights public supply wells.
Vietzke Village Residents
The supply wells for the Vietzke Village are officially abandoned and no longer a source ofexposure. Past exposure to TCE in Vietzke Village drinking water represents no apparent publichealth hazard to the general population. However, an indeterminate public health hazard existsfor the children of women exposed while pregnant to TCE in Vietzke Village drinking water priorto August 1989 when exposure ceased.
Children born to women who drank Vietzke Villagewater while pregnant prior to August 1989 could have been at some risk for birth defects or otheradverse birth outcomes. There is no clear evidence, however, to indicate that the levels of TCEexposure at Vietzke Village were high enough to cause these types of health effects.
Past exposure to nitrate in Vietzke Village drinking water represents no apparent public healthhazard to the general population. Levels of nitrate in the Vietzke wells could have causedmethemoglobinemia in infants only if additional risk factors were present such as stomachinfection, diarrhea or high dietary nitrate intake. An indeterminate health hazard exists for thechildren of women exposed while pregnant to nitrate in Vietzke Village drinking water. Inconclusive evidence suggests that levels of nitrates similar to those found in the Vietzke wellscan cause adverse birth outcomes.
Current and past exposure to TCE in the Airway Heights public supply wells represents noapparent public health hazard.
Airway Heights Residents
The Airway Heights public supply wells continue to be monitoredby the base and show very low levels of TCE that are below regulatory standards.
The supply wells for the Scafco Corporation are officially abandoned and no longer a source ofexposure. Past exposure to TCE in the Scafco Corporation supply wells represents no apparentpublic health hazard.
The Craig Road Landfill covers approximately 100 acres of base property along Craig Roadapproximately 0.7 miles south of U.S. Route 2 and 0.5 miles east of the main base. Operated asthe main landfill for the base from the late 1950s through the late 1970s, it received variouswastes including sanitary refuse, industrial waste, and construction debris. The RemedialInvestigation/Feasibility Study completed for the Craig Road Landfill in September 1992described two specific source areas within the landfill: the northeast area covering approximately6 acres and the southwest area of about 13 acres. Both areas received waste via trench-and-fill atdepths greater than 30 feet. A third area covering about 30 acres in the southeast corner isthought to have received only inert, solid materials (e.g., concrete). In addition to the fill areas,the landfill was also the site of the base sanitary wastewater treatment plant. This plant receivedsanitary wastewater from housing units and the base hospital as well as industrial waste frommaintenance shops. Treated water was discharged to a surface evaporation/percolation pond andto underground trenches. Occasionally, treated wastewater was spread on the fill areas to helpcompact the waste. The treatment plant ceased operation in November 1993 (see Figure 5).
A substantial remedial effort has been undertakento address volatile organic compounds (VOCs) in groundwater originating from the two identifiedsource areas of the landfill. A geo-textile liner(cap) now covers the landfill to prevent rainwaterinfiltration that could carry more contaminants intothe groundwater. Also, a groundwater pump-and-treat system was installed in September 1995 andis currently operating at the site to removecontaminants from groundwater and preventmovement to off-base areas.
The Craig Road Landfill is the source of groundwater contamination that has affected VietzkeVillage public water supply wells and Scafco Corporation water supply wells. The landfill is alsoa potential contributing source of the groundwater contamination currently affecting AirwayHeights public supply wells. Groundwater flow is estimated to be moving east/northeast from thelandfill in both the shallow (alluvial) and bedrock (basalt) aquifers. Bedrock groundwater in thisarea is part of the Wanapum Basalt aquifer and is divided into an upper flow region (Basalt A)and deeper flow region (Basalt B) by a layer of mostly impermeable sedimentary rock (InterbedA). Bedrock groundwater flow in the Craig Road Landfill area was measured at a range of 0.3-8.6 feet per day for Basalt A and 8 feet per day for Basalt B.
Most of the contamination detected in and aroundthe landfill has been found in the upper Basalt Abedrock flow. Interbed A is not completelyimpermeable, however, and can allow groundwaterand contaminants to move into the deeper Basalt Bflow. It is possible, therefore, for contaminants tomove from the ground surface of the landfill throughthe shallow aquifer into the Basalt A flow and thenthrough fractures into the deeper Basalt B flow. TheBasalt B region of the Wanapum Basalt aquifer isseparated from the deeper Grande Ronde Basaltaquifer by another layer of sedimentary rock(Interbed B). No drinking water or monitoring wells in this area are located in the Grand Ronde aquifer.
Figure 6 shows the outline of a TCE plume moving from the two identified source areas in thelandfill. In April 1991, a maximum of 2,800 ppb TCE was detected in monitoring well MW-85located in the Basalt A bedrock flow just across the north perimeter of the landfill. The maximumcontaminant level (MCL) for TCE is 5 ppb. Although several other VOCs were detected in soilgas samples, TCE is the only groundwater contaminant migrating off-base at levels of concern. TCE originating from the landfill has impacted drinking water wells at the Vietzke Village trailerpark, Scafco supply wells and possibly the Airway Heights public supply wells. These threepoints of exposure are discussed below.
Vietzke Village Residents
Vietzke Village is a 55-60 unit trailer park located along the northeast border of the Craig RoadLandfill. The land originally contained only one residence until 1968 when the trailer park wasstarted. Drinking water for trailer park residents was formerly supplied by three blended, openbore-hole wells (RW-9, RW-10 and RW-11) located on the park grounds as indicated in Figures 5and 6. According to the owner, the wells were installedbetween the late 1960s and early 1970's. RW-11 servedas the primary source of drinking water for VietzkeVillage. RW-10 and RW-9 were primarily used forirrigation and laundry but also served as drinking watersupply wells during times of high use. Specifics on thetype and rates of water use from these wells are notavailable.
Initial sampling and analysis for VOCs in July 1989detected only TCE at a maximum level of 80 ppb in well RW-9. The most recent sampling inJune 1991 detected maximum levels of TCE at 59 ppb (RW-11) and tetrachloroethylene (PCE) at0.6 ppb (RW-9). Fairchild provided bottled drinking water to residents of the park from July, 18through early August 1989 when the park was connected to the Fairchild water supply. 14 Allthree wells were officially abandoned between May and June 1993. The TCE sampling results for the Vietzke wells are given in
Table 4. below. Vietzke Village Supply Well TCE Measurements
* Two values represent duplicate samples.
NOTE: Wells no longer in use as of August 1989.
TCE is the only contaminant of concern related to the Craig Road Landfill that has been detectedin the Vietzke wells. However, nitrate was also found at elevated levels in the Vietzke watersupply. Samples taken between September 1982 and May 1988 showed elevated nitrates with amaximum of 10.5 ppm detected in January 1986. It is not know from what point in the Vietzkewater distribution system these samples were taken. A maximum of 19.2 ppm nitrate was alsodetected in monitoring well MW-80 located in the Vietzke Village trailer park. Although thesource of this nitrate contamination is unknown, the RI noted that MW-80 is located near theVietzke septic field. Septic fields, landfills and agricultural runoff are common sources of nitratecontamination in drinking water wells. In general, only shallow wells are at risk for nitratecontamination. However, the improperly cased bedrock wells at the Vietzke Village weresusceptible to contaminants moving from the shallow aquifer. Nitrate levels detected inmonitoring wells located near the landfill indicate that the landfill is not a substantial source ofnitrate.
There is currently no exposure of Vietzke Village residents to TCE or nitrate in drinking watersince water is now supplied by the base. Past exposure occurred via ingestion, skin contact andinhalation of vapors (TCE only). Exposure via ingestion ceased when the base supplied residentswith bottled drinking water. Inhalation of TCE vapor ceased when the village was supplied withbase water.
Specific contributions of each well to the overall drinking water supply are not available. Tapwater samples were reportedly taken from Vietzke Village residences but this data could not belocated. In order to be protective of public health, it was assumed that Vietzke Village residentswere exposed to the maximum level of TCE detected in the primary supply well (RW-11 at 79ppb). Exposure to nitrates was estimated using the maximum level detected of 10.5 ppm. Theperiod of concern for past exposure of Vietzke Village residents could have extended from 1968when the trailer park first started through July 1989 whenexposure ceased.
Additional exposure of Vietzke residents to TCE occurred as aresult of landfill emissions from soil into air. The dose receivedfrom breathing TCE in air emitted directly from the landfill wascalculated using estimated air levels derived from mathematicalmodels. The contribution of this pathway to the overallexposure of Vietzke residents to TCE is very small and does notaffect the dose comparisons made below. Current and pastexposure of Vietzke residents to landfill gases is addressedseparately as completed exposure pathway 1b (page 28).
Past exposure to TCE in Vietzke Village drinking water is not expected to pose a non-cancerrisk for the general population. There is a concern that children born to women who drankVietzke Village water while pregnant prior to August 1989 could have been at some risk forbirth defects and other adverse birth outcomes. There is no clear evidence, however, toindicate that the levels of exposure at Vietzke Village were high enough to cause these typesof health effects. There is no current exposure to TCE in drinking water at the VietzkeVillage.
The estimated dose from the maximum level of TCEdetected in primary supply well RW-11 (79 ppb) isbelow ATSDR's acute oral minimal risk level (MRL)for TCE. This means that short-term exposure (i.e.,less than two weeks) is not of concern. EPA has notprovided a chronic oral reference dose (RfD) and nointermediate or chronic oral MRLs are available withwhich to evaluate longer-term exposure to TCE. Apreviously available intermediate oral MRL for TCEhas been withdrawn as of November 1997. Thepotential for non-cancer health effects from longer-termexposure was based, therefore, on available data fromhuman and animal studies.
One animal study determined that rats exposed to high doses of TCE in drinking water whilepregnant gave birth to offspring with heart defects. Although this study has been criticized, itrepresents the most sensitive toxic endpoint of TCE exposure and is supported by limitedevidence in humans. 15 The lowest-observed adverse effect level (LOAEL) from this studywas compared with the estimated dose received by a pregnant woman exposed to 79 ppb TCEin drinking over a 9-month period. The estimated dose was approximately 35 times belowthis LOAEL. This dose was based on an assumption of 2 liters of drinking water ingested perday combined with an equivalent dose from skin absorption and inhalation of TCE as a resultof showering, bathing and other indoor water use. This comparison indicates that TCE in theVietzke wells would not have been of concern.
It is important to consider, however, that some human studies have associated TCE exposurewith birth defects in children as a result of exposure prior to birth (i.e., in utero exposure). The birth defects identified included heart malformations, neural tube defects and oral clefts. Other adverse birth outcomes reported include decreased fetal weight and increased fetaldeath. The levels at which pregnant mothers were exposed in these studies are not welldefined. Some exposures appear to have been substantially higher than the levels measured atVietzke Village while others are similar. These studies are suggestive of an associationbetween TCE exposure and developmental effects but are not sufficient to allow an accurateestimate of what the risk might have been for Vietzke Village residents. Further study mayshow no association between the levels of TCE in the Vietzke wells and developmentaleffects. More discussion of the non-cancer effects of TCE is given in the ToxicologicalSummaries section (page 51).
Also of concern is the potential that levels of TCE in the Vietzke wells may have been higherin the past. Although no data exists prior to July 1989 when these wells were first sampled,levels of TCE may have been higher in the past. Each of the three supply wells is locatedapproximately 800 feet downgradient of monitoring well (MW-85) that showed considerablevariation in TCE levels with no established trend. Such variation could also have occurred inthe Vietzke wells. Since an exposure duration as short as the first trimester of pregnancycould be of concern, short-term increases in TCE levels could be important. Any fluctuationsin the Vietzke wells, however, would not likely have reached levels found in MW-85 becauseof the expected dilution of TCE moving from Basalt A into uncontaminated water from the relatively clean Basalt B aquifer.
The suggestive nature of the humans studies associating TCE in drinking water with birthdefects, along with the possibility that exposures may have been higher prior to initialsampling, is cause for concern. Babies born to women who drank Vietzke water whilepregnant prior to August 1989 may have been at risk for birth defects and other adverse birthoutcomes. The small and transient nature of the population at Vietzke Village make it anunlikely candidate for a study aimed at evaluating birth defects. Any residents living atVietzke Village during the period of concern (1968 through July 1989) can contact RobertDuff (DOH) toll-free at 1-888-5TOXICS (1-888-586-9427) or ATSDR at 800-447-1544 formore information.
Nitrate in Vietzke Village drinking water is not expected to result in non-cancer health effectsto the general population. Exposure of infants to formula prepared with Vietzke Villagedrinking water prior to August 1989 could have resulted in methemoglobinemia only ifexposure was accompanied by other risk factors such as stomach infection, diarrhea or highdietary nitrate intake. An indeterminate health hazard exists for the children of womenexposed while pregnant to nitrate in Vietzke Village drinking water. Inconclusive evidencesuggests that levels of nitrates similar to those found in the Vietzke wells can cause adversebirth outcomes.
The estimated dose for an infant ingesting 0.6 liters per day of formula prepared with 10.5ppm nitrate contaminated water is equivalent to the RfD for nitrate. This RfD is based on astudy that found no methemoglobinemia in infants at drinking water levels below 10 ppmwhile 2 % of the infants exposed at 11-20 ppm showed early clinical signs of this disorder. Most studies show that levels below 20 ppm will not result in symptoms or adverse healtheffects unless accompanied by a large dietary source or simultaneous exposure to bacteria thatcan enhance the conversion of nitrate to nitrite in the digestive tract. 16
The estimated dose resulting fromexposure via ingestion, skin contact and inhalation to the maximum level ever detected in theAirway Heights public supply wells (3.2 ppb) is 900 times below the LOAEL. This dose wascalculated assuming a 9-month exposure of a pregnant woman drinking 2 liters of water perday combined with an equivalent dose from skin absorption and inhalation as a result ofshowering, bathing and other indoor water use. This LOAEL is based on developmental heartdefects in rats and represents the most sensitive health effect yet found in animal studies.
A dose was estimated using the maximum levelof TCE (3.2 ppb) ever detected in Airway Heights public water supply. Exposure viaingestion, skin contact and inhalation was assumed to occur over a 30-year period of a childgrowing to adulthood. The estimated cancer risk calculated for this scenario was determinedto be insignificant. The cancer effects of TCE are discussed in the Toxicological Summaries section.
Non-cancer adverse health effects are not expected to result from past exposure to TCE inthe Scafco water supply wells. Workers were assumed to be exposed to 2 ppb TCE viaingestion of drinking water from RW-7 at a rate of 2 liters of water ingested per day. Theestimated dose resulting from this exposure is 2,800 times below the LOAEL. This estimateddose assumed a worst-case scenario of a pregnant woman exposed over a 9-month period andso will be protective of all workers. This LOAEL is based on developmental heart defects inrats and represents the most sensitive health effect yet found in animal studies.
The TCE ambient air level predicted for the VietzkeVillage is 50 times below the intermediate MRL for inhalation exposure. This MRL is basedon decreased heart rate and sleep effects in rats following high levels of exposure to TCE inair. The additional exposure of Vietzke Village residents from landfill emissions of TCE wasalso considered in combination with the oral and inhalation exposure evaluated for TCE indrinking water. The added exposure estimated by the model was determined to add only asmall percentage to the overall dose. The potential for non-cancer health effects from pastexposure of Vietzke Village residents to TCE in drinking water is discussed as completedexposure pathway 1a (page 16).
The reader should be awarethat people living in the Vietzke Village for many years prior to August 1989 were exposed toTCE in drinking water at levels estimated to pose a slight increase in cancer risk. Thisexposure is discussed as completed exposure pathway 1a (page 16). In addition to thisestimated cancer risk, DOH performed a crude analysis of cancer incidence in the VietzkeVillage zip code (i.e., 99022). Of all the cancer types evaluated only lung cancer showed anincrease when compared with statewide rates. It is unlikely that this slight increase in lungcancer is related to TCE exposure. The results and limitations of this analysis are given in theHealth Outcome Data section (page 55). The cancer effects of TCE are discussed further inthe Toxicological Summaries section (page 51).
. A dose was estimated using the maximum levelof TCE (1.5 ppb) ever detected in West Thorpe Road residential wells. Exposure viaingestion, skin contact and inhalation was assumed to occur over the 30-year period of a childgrowing to adulthood. The estimated cancer risk calculated for this scenario was determinedto be not significant. The cancer effects of TCE are discussed in the Toxicological Summaries section (page 55).
: No-Name Ditch (Fairchild Easement) --> Sediment/Surface Water --> West Thorpe Road Area Residents
Theestimated dose calculated for a child exposed viaingestion of and skin contact with maximum detectedlevels of metals in ditch sediment did not exceed anyMRLs or RfDs. It was assumed that an older child mightplay in and around the ditch 120 days per year over aperiod of 10 years. No MRLs or RfDs are currentlyavailable with which to compare estimated doses to magnesium or aluminum. The 90thpercentile values of these two metals derived from the final round of sampling in the ditch inNovember 1991 do not exceed the 90th percentile background levels published by Ecology. 30 Exposure to magnesium and aluminum in ditch sediment and surface water will not, therefore, result in substantial exposure.
|: Tordon --> Groundwater/Soil --> West Thorpe Road Area Residents|
|: On-Base Activities --> Sediment/Soil --> Fairchild Personnel|
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